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Drug Profile

The information on this site is intended to supplement and enhance, not replace, the advice of a physician who is familiar with your medical history. Decisions about your health should always be made ONLY after detailed conversation with your doctor.

Generic drug name: acetaminophen (a seat a MEE noe fen)
GENERIC: available FAMILY: Non-Narcotic Painkillers
Find the drug label by searching at DailyMed.

Pregnancy and Breast-feeding Warnings [top]

Pregnancy Warning

Acetominophen crosses the placenta and exposes the fetus to the drug. Tell your doctor if you are pregnant or thinking of becoming pregnant before you take this drug.

Breast-feeding Warning

Acetaminophen is excreted in human milk. You should consult with your doctor if you are planning to nurse.

Safety Warnings For This Drug [top]


There have been a number of case reports of liver damage involving a possible drug interaction between isoniazid, a medication used to prevent and treat tuberculosis (TB), and acetaminophen, an over-the-counter painkiller and the active ingredient in Tylenol. Isoniazid alone, especially as people get older, has been documented to cause liver damage. Acetaminophen, alone in large doses or probably in combination with alcohol, also increases the risk of liver damage. The combination of acetaminophen with isoniazid, according to the authors of these case reports, may also be dangerous.

If you are taking isoniazid for tuberculosis or have a positive TB skin test and are using the drug, consult your physician before using acetaminophen or any combination product containing acetaminophen. Discuss alternatives to acetaminophen with your physician.

Drug Interaction Warning

Increased Risk of Bleeding When Acetaminophen and Warfarin (COUMADIN) Are Taken Together

Acetaminophen may interact with warfarin to increase the risk of bleeding. This risk increases with increasing doses of acetaminophen. The risk of bleeding has been found to increase tenfold in people who were taking 28 or more regular-strength acetaminophen tablets per week, or the equivalent of 18 or more extra-strength tablets per week, compared to those taking warfarin and no acetaminophen.[1] A regular-strength tablet contains 325 milligrams of acetaminophen, and an extra-strength tablet contains 500 milligrams of the drug.

Warfarin is a drug of considerable benefit after heart valve replacement and in preventing blood clots from a type of heart rhythm disturbance known as atrial fibrillation. It also reduces the risk of death, recurrent heart attacks, and stroke after a heart attack.

Based on this new evidence, if you are taking warfarin, you should notify your doctor before taking any product containing acetaminophen.

Facts About This Drug [top]

Like aspirin, the painkiller acetaminophen (TYLENOL) reduces pain and fever. Unlike aspirin, it does not help the redness, stiffness or swelling associated with inflammation. Because of this, aspirin (EASPRIN, ECOTRIN, EMPIRIN, GENUINE BAYER ASPIRIN) is much more effective for treating the inflammation of arthritis.[2]

However, one advantage of acetaminophen over aspirin is that acetaminophen does not cause the stomach bleeding that aspirin can cause.

For this reason, doctors often...

Like aspirin, the painkiller acetaminophen (TYLENOL) reduces pain and fever. Unlike aspirin, it does not help the redness, stiffness or swelling associated with inflammation. Because of this, aspirin (EASPRIN, ECOTRIN, EMPIRIN, GENUINE BAYER ASPIRIN) is much more effective for treating the inflammation of arthritis.[2]

However, one advantage of acetaminophen over aspirin is that acetaminophen does not cause the stomach bleeding that aspirin can cause.

For this reason, doctors often prescribe or recommend acetaminophen to people who are likely to suffer from bleeding when they take aspirin. This includes most people taking blood-thinning drugs like warfarin (COUMADIN) or heparin, because although the combination of acetaminophen and blood-thinning drugs can cause bleeding, it appears to occur less commonly than with aspirin. Also included in this group are people who have ulcers, gout or bleeding problems such as hemophilia.

People who are allergic to aspirin often can take acetaminophen.

Using acetaminophen to treat a fever

In general, patients should not take anything to reduce a fever until the cause of the fever is known. It is rarely necessary to treat a fever. However, if a fever is having harmful effects or is causing extreme discomfort, it can be reduced with acetaminophen. When taking acetaminophen to reduce a fever, take it regularly every four to six hours, and stop taking it when the underlying problem is gone or has been controlled through other treatment.

Adverse effects

There is the potential for allergic reactions (swelling of the face, mouth and throat; difficulty breathing; itching; or rash) with acetaminophen.

Acetaminophen and pregnancy

A meta-analysis (a study that combines data from many other studies) found that there was an increased risk of childhood asthma when acetaminophen was used during pregnancy. Based on these results, the authors recommended further research to determine recommendations that should be considered when treating patients.[3]

In 2016, the International Journal of Epidemiology published an article showing a slight increase in the risk of childhood asthma when acetaminophen was used by mothers during pregnancy or by infants up to age 6 months.[4]


Frequent use of medication to manage headache pain may lead to a condition known as medication overuse headache (MOH). According to a review published in the August 2004 issue of the medical journal Lancet Neurology,[5] there now is substantial evidence that all drugs used for the treatment of headache can cause MOH in patients who are using drugs to treat their headache. Even simple painkillers such as aspirin and acetaminophen can induce MOH.

Patients experiencing MOHs should discuss with their doctors the important details of their headaches and, depending on their individual case, the type of withdrawal from the MOH-causing drugs that is best for them.[6]

Liver damage and liver failure

Acetaminophen can cause liver damage, which sometimes can be fatal. Research published in the December 2005 issue of the medical journal Hepatology found that the annual percentage of potentially fatal acute liver failure cases caused by acetaminophen rose from 28% in 1998 to 51% in 2003.[7]

Research published in 2006 in the Journal of the American Medical Association (JAMA) further supports this finding. The JAMA research showed that healthy medical study participants given the maximum approved daily dose of acetaminophen developed an early sign of possible liver damage.[8] The maximum recommended dose was then 4.0 grams (g) (4,000 milligrams [mg]) per day, equivalent to two extra-strength acetaminophen tablets taken four times per day. These results are of particular concern because the people in the study were not drinking any alcoholic beverages. When combined with alcohol, this dose of acetaminophen would have further increased their liver toxicity.

In 2021, a research study in Hepatology showing that use of acetaminophen at the recommended dose for four days or longer was associated with liver damage in patients who drank alcohol excessively (drinking at least two alcoholic drinks daily) or fasted (not eating for at least 24 hours).[9]

Acetaminophen overdose and idiosyncratic adverse drug reactions involving the liver have replaced viral hepatitis (inflammation of the liver) as the most frequent apparent causes of acute liver failure in the United States.[10],[11] Patients must be careful to examine the list of ingredients in their medications because many prescription and over-the-counter drugs contain acetaminophen, although this may not be apparent from the brand name. Patients have overdosed from unsuspected use of two different acetaminophen products.

Some drug safety experts, including Public Citizen's Health Research Group, have argued that measures including limiting over-the-counter package size and restricting the prescription of narcotic-acetaminophen combinations (or to separate the narcotic from the acetaminophen) may be necessary to reduce the incidence of acetaminophen-induced liver toxicity.[7]

Interactions with other drugs

Results published from a prospective, randomized, double-blind, placebo-controlled study of 45 patients found that acetaminophen (at a dose of 2-3 g a day, administered for 10 days) increased the anticoagulant effect of warfarin in stable patients treated with warfarin.[12] (See drug interaction warning at the top of this profile: “Increased Risk of Bleeding When Acetaminophen and Warfarin [COUMADIN] Are Taken Together.”)

Studies show ...

The Medical Letter on Drugs and Therapeutics published an article in which the authors looked at the effectiveness of acetaminophen in doses of 1,000 mg versus 650 mg in treating mild-to-moderate pain from such conditions as osteoarthritis and headache. According to the article, no published data showed that the 1,000-mg dose was more effective than the 650-mg dose.[13]

The British Journal of Clinical Pharmacology published an article on the risk of mortality and the unintentional overdose of acetaminophen. The data examined in the study showed that the unintentional overdose of acetaminophen in patients was associated with severe acute (sudden) liver injury.[14]

In 2015, a meta-analysis combining data from 13 randomized clinical trials published in The British Medical Journal showed that acetaminophen had a small and short-term effect in patients with osteoarthritis of the hip or knee, but was ineffective in patients with low-back pain.[15]

In 2016, the Cochrane Database published a review showing that acetaminophen was no more effective than a placebo in treating patients with acute low-back pain and did not improve quality of life or physical function.[16]

In 2016, the Journal of the American Medical Association — Pediatrics (JAMA Pediatrics) published an article showing an increased risk of behavioral problems in children when acetaminophen was used during pregnancy.[17]

Regulatory actions surrounding acetaminophen

2009: On June 29 and 30, the Food and Drug Administration (FDA) held a public advisory committee meeting to address the concerns of liver injury in relation to the use of acetaminophen in both prescription and non-prescription products. The FDA considered the recommendations made by the advisory committees in order to demand interventions and take additional steps to reduce the number of cases of acetaminophen-related liver injury.

2011: In January, the FDA issued an advisory concerning the strength of acetaminophen in prescription-drug products. The FDA requested that drug manufacturers limit the strength of acetaminophen in prescription-drug products to 325 mg per tablet. The agency required a black-box warning be added to the drug label of all acetaminophen-containing prescription products that would highlight the potential for severe liver injury. The agency stated that another warning highlighting the potential for allergic reactions (swelling of the face, mouth and throat; difficulty breathing; itching; or rash) would also be added to the drug label. The makers of TYLENOL have recommended reducing the maximum daily dose of acetaminophen from 4 to 3 g.[18]

2013: In August, the FDA issued an advisory that acetaminophen was found to be associated with a risk of rare but serious, potentially fatal skin reactions, such as Stevens-Johnson Syndrome. According to the advisory, the skin reactions can occur at any time after starting treatment with the drug.[19]

2014: In January, the FDA issued another advisory on the dosage of acetaminophen. The FDA recommended the discontinuation of prescribing and dispensing of prescription combination drug products that contain more than 325 mg of acetaminophen per tablet. There are no available data to show that taking more than 325 mg of acetaminophen per dosage unit provides additional benefits that outweigh the added risks for liver injury.[20] Unfortunately, the FDA has not yet ordered the reduction of the more widely used over-the-counter versions of acetaminophen from 500 mg to 325 mg.

Before You Use This Drug [top]

Tell your doctor if you have or have had:

  • allergies to acetaminophen or aspirin
  • pregnancy or are breast-feeding
  • alcohol dependence
  • liver problems
  • viral hepatitis
  • kidney problems
  • phenylketonuria
  • diabetes (drug can interfere with blood glucose tests)

Tell your doctor about any other drugs you take, including aspirin, herbs, vitamins, and other nonprescription products.

When You Use This Drug [top]

  • If taking for pain, including arthritic pain, and pain persists for longer than 10 days or condition becomes worse, or new symptoms occur, or the painful area is red or swollen, contact your doctor.
  • If taking for fever, and fever persists for longer than three days, condition becomes worse, or new symptoms occur, contact your doctor.
  • If taking for sore throat, and sore throat is severe, persists for longer than two days, or occurs together with or is followed by fever, headache, rash, nausea, or vomiting, contact your doctor.
  • Avoid use of alcohol if taking more than an occasional one to two doses.
  • Get emergency help if you suspect an overdose, even if no symptoms have appeared. Treatment started 24 hours following overdose may not work in prevent liver damage or death.

If you suspect an overdose, call this number to contact your poison control center: (800) 222-1222.

How to Use This Drug [top]

  • If you miss a dose, take it as soon as you remember, but skip it if it is almost time for the next dose. Do not take double doses.
  • Do not share your medication with others.
  • Take the drug at the same time(s) each day.
  • Store at room temperature with lid on tightly. Do not store in the bathroom. Do not expose to heat, moisture, or strong light. Keep out of reach of children.

Interactions with Other Drugs [top]

The following drugs, biologics (e.g., vaccines, therapeutic antibodies), or foods are listed in Evaluations of Drug Interactions 2003 as causing “highly clinically significant” or “clinically significant” interactions when used together with any of the drugs in this section. In some sections with multiple drugs, the interaction may have been reported for one but not all drugs in this section, but we include the interaction because the drugs in this section are similar to one another. We have also included potentially serious interactions listed in the drug’s FDA-approved professional package insert or in published medical journal articles. There may be other drugs, especially those in the families of drugs listed below, that also will react with this drug to cause severe adverse effects. Make sure to tell your doctor and pharmacist the drugs you are taking and tell them if you are taking any of these interacting drugs:

INH, isoniazid.

Adverse Effects [top]

Call your doctor immediately if you experience:

  • yellow eyes or skin
  • bloody or cloudy urine
  • fever with or without chills
  • trouble urinating, painful urination, or sudden decrease in amount of urine
  • skin rash, hives, or itching
  • unexplained fever or sore throat
  • unusual bleeding or bruising
  • unusual tiredness or weakness
  • bloody or black, tarry stools
  • severe lower back or side pain
  • pinpoint red spots on skin
  • sores, ulcers, or white spots on lips or in mouth

Signs of overdose:

  • diarrhea
  • loss of appetite
  • nausea or vomiting
  • pain or cramps in stomach
  • pain, tenderness, and/or swollen upper abdomen
  • abnormal increase in sweating

If you suspect an overdose, call the following number to contact your poison control center: (800) 222-1222.

Periodic Tests[top]

Ask your doctor which of these tests should be done periodically while you are taking this drug:

  • iver function tests, for long-term or high-dose therapy

last reviewed February 29, 2024